The Stoics believed it to be the only vital force in the universe. It also features in systems of eastern philosophy in the Brahman-Atman of Hinduism, and in the School of Yin-Yang, Taoism, and Neo-Confucianism as qi. Similar concepts were held by hermetic philosophers like Paracelsus, and by Baruch Spinoza, Gottfried Leibniz and later by Friedrich Schelling (1775-1854). It has been elaborated since the 1960s by Gaia theorists such as James Lovelock.